After cameras as mass-produced models, each of which includes an auto focusing function, have first come to the market in 1977 from Konica, a variety of auto focusing technologies applying mechanical and non-mechanical systems have been developed. Further, several technologies for depth estimation of subjects using stereo camera technology, time of flight technology, structured technology, and the like may have been developed.
Conventional auto focusing technology may be roughly classified as an active system or a passive system. Since an ultrasonic or infrared generator is needed in the active system divided into a system using ultrasonic waves and a system using infrared rays, relatively large amounts of additional power may be required. If there is a window between a camera and a subject or if the camera and the subject are in a very distant place or are close to each other, focus may fail to be made.
The passive system may be an autofocus rangefinder system, a contrast detection system, a phase-difference detection system, or the like. The autofocus rangefinder system may be a system of extracting a depth through a method of performing coincidence of stereo images based on a triangulation principle and performing auto focusing in a rangefinder camera. The contrast detection system may be an auto focusing system currently used in most compact digital cameras and may be a system of continuing calculating contrasts of some of images while moving a lens and determining that focus is made if there is a maximum contrast value. The phase-difference detection system may divide light incident through a lens into one pair and compare a pair of lights to determine whether focus is made. For this purpose, a sensor for phase-difference detection should be used additionally, or a sensor of a dual pixel structure should be used.
However, the autofocus rangefinder system should perform auto focusing using an image obtained by an additional structure which is a rangefinder rather than an image captured by a camera. Since the contrast detection system calculates a contrast between images while continuing moving a lens, it takes a long time to perform auto focusing. If a phase-difference detection sensor is separately used in the phase-difference detection system, since a very precise array is needed, there may be a problem in mass production and quality management and it may be difficult to be applied to a micro-camera such as a mobile phone camera. Further, sensor costs may be increased in a system for phase-difference detection using a dual pixel sensor, particularly, a micro-camera have a technical problem in implementing the dual pixel sensor on a trend where an image sensor pixel becomes smaller and smaller in size.
Stereo camera technology which is one of technologies for depth estimation for a subject may be a manner of installing two optical systems at a constant distance, obtaining images of the subject from sensors of the two optical systems, and comparing a disparity between the two images to estimate a depth. Since this manner obtains images using the two different sensors, a synchronization process between the two images may be needed and costs for a precise array and image adjustment for the synchronization process may be needed.
Further, the time of flight technology and the structured light technology among technologies for depth estimation of a subject may be technologies of irradiating rays such as infrared rays and estimating a depth using a detector. It may be difficult for the time of flight technology and the structured light technology to be used outdoors. The time of flight technology and the structured light technology may have much power consumption.
Thus, a multi-aperture camera system having an auto focusing function and/or a depth estimation function for solving disadvantages and problems of conventional auto focusing technology and/or conventional depth estimation technology is proposed.